Systems, methods, and devices for locating items, people, and/or animals

ABSTRACT

Systems, methods, and devices for locating items, people, and/or animals are provided. In accordance with some embodiments, locator devices for locating a target device are provided, the locator devices comprising: a first transceiver configured to communicate with a second transceiver in the target device; a Global Navigation Satellite System (GNSS) receiver configured to receive data from a plurality of satellites for calculating a location; a visual indicator; and a hardware processor that: receives signals from the first transceiver; calculates an estimated distance between the locator device and a target device based on the signals; controls whether the GNSS receiver is powered on or off based on the estimated distance; and causes the visual indicator indicate an estimated direction to the target device from the locator device.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/894,623, filed Feb. 12, 2018, now U.S. Pat. No. 10,460,584, which isa continuation of U.S. patent application Ser. No. 15/173,239, filedJun. 3, 2016, now U.S. Pat. No. 9,892,610, which claims the benefit ofU.S. Provisional Patent Application No. 62/171,213, filed Jun. 4, 2015,each of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND

Items, people, and animals frequently become lost from people who wantto know the location of the items, people, and animals. For example, aparent may want to know the location of a child that has wondered awayfrom the parent.

Accordingly, new systems, methods, and devices for locating items,people, and/or animals are desirable.

SUMMARY

Systems, methods, and devices for locating items, people, and/or animalsare provided. In accordance with some embodiments, locator devices forlocating a target device are provided, the locator devices comprising: afirst transceiver configured to communicate with a second transceiver inthe target device; a Global Navigation Satellite System (GNSS) receiverconfigured to receive data from a plurality of satellites forcalculating a location; a visual indicator; and a hardware processorthat: receives signals from the first transceiver; calculates anestimated distance between the locator device and a target device basedon the signals; controls whether the GNSS receiver is powered on or offbased on the estimated distance; and causes the visual indicatorindicate an estimated direction to the target device from the locatordevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example of a system architecture inaccordance with some embodiments.

FIG. 2 is a block diagram of an example of a locator device inaccordance with some embodiments.

FIG. 3 is a block diagram of an example of a target device in accordancewith some embodiments.

FIG. 4 is an illustration of an example of a user interface of a locatordevice in accordance with some embodiments.

FIG. 5 is a flow diagram of an example of the operation of an example ofa system in accordance with some embodiments.

FIG. 6 is an illustration an example of a target device locationtechnique in accordance with some embodiments.

DETAILED DESCRIPTION

Systems and methods (hereinafter collectively “mechanisms”) for locatingitems and/or people are provided. In some embodiment, these mechanismscan be used to locate any suitable item (e.g., such as bag), person(e.g., such as a child, a mentally handicapped person), animal (e.g.,such as a pet), or anything else capable of having a target device (asdescribed herein) attached thereto.

In some embodiments, the mechanisms can include a locator device that isused to monitor and find the location of a target device. The locatordevice and the target device can be implemented in any suitable form.For example, the locator device and the target device can be implementedas a stand-alone system comprising two handheld devices, each havinginternal electronics, a visual indicator mechanism (e.g., such as adisplay or LED indicator lights), an audio generating mechanism (e.g.,such as an amplifier, a speaker, and/or a headphone jack), and a userinput mechanism (e.g., such as buttons and/or a touch screen interface).As another example, the locator device can be implemented as a two-partapparatus that includes a mobile computing device (e.g., such as asmartphone, a tablet computer, a laptop computer, a smart watch, etc.)and a transceiver device that can communicate with the mobile computingdevice (e.g., via a wired or wireless interface (e.g., Bluetooth, Wifi,etc.).

Turning to FIG. 1, a block diagram 100 of an example of hardware forimplementing the mechanism is provided. As shown, the locator device canbe implemented as a handheld device (“fob”) 102 and the target devicecan be implemented as a wearable device (“wearable”) 104. Both the foband the wearable can include a Global Navigation Satellite System (GNSS)system receiver (for receiving signals from GNSS satellites 106), aradio transceiver (e.g., a 915 MHz (or any other suitable frequency orcombination of frequencies transceiver)), a processor (e.g., amicrocontroller, a microprocessor, a digital signal processor, etc.),and a power source. The fob can also include an electronic compass (orany other suitable orientation detection mechanism) and an LED display(or any other suitable output mechanism). In some embodiments, thewearable can also include an electronic compass (or any other suitableorientation detection mechanism) and an LED display (or any othersuitable output mechanism).

Although the mechanisms are described herein as using a GNSS receiver(and GNSS satellites), it should be apparent that any suitable positionlocation mechanism (e.g., such as radio signal triangulation, cell phonesignal triangulation, etc.) can be used.

A more detailed illustration of an example of a locator device inaccordance with some embodiments is shown in FIG. 2. As illustrated, insome embodiments, the locator device can include a microcontroller, abattery, a DC to DC converter, a piezo buzzer, a vibration motor, abutton matrix, a display, a magnetometer/accelerometer, a programminginterface, a GNSS receiver, a GNSS receiver antenna, a radiotransceiver, a radio transceiver antenna, and/or any other suitablecomponents.

A more detailed illustration of an example of a target device inaccordance with some embodiments is shown in FIG. 3. As illustrated, insome embodiments, the target device can include a microcontroller, a USBport, a battery charger, a battery, a DC to DC converter, a piezobuzzer, a magnetometer/accelerometer, a programming interface, a GNSSreceiver, a GNSS receiver antenna, a radio transceiver, a radiotransceiver antenna, a radio receiver impedance match circuit, and/orany other suitable components.

In some embodiments, the microcontrollers shown in FIGS. 2 and 3 caninclude programmable non-volatile memory for storing programinstructions for controlling the operation of the microcontrollers. Anysuitable amount and type of memory can be provided in some embodiments.In some embodiments, the locator device and the target device canadditionally or alternatively include separate non-volatile memory(e.g., for storing program instructions) and volatile memory (e.g., forstoring transient data).

In accordance with some embodiments, the locator device and the targetdevice can perform the following:

-   -   1. On the locator device, a user interface can be provided that        allows a user to select a maximum distance (“safe zone”) within        which the target (e.g., the item, person, animal, etc. to which        the target device is attached) is allowed to be from the locator        device without a warning being produced.    -   2. A radio link between the radio transceivers of the locator        device and the target device can be turned ON and a maximum        distance between their transceivers estimated using received        signal strength indication (RSSI). This distance can be measured        by solving for distance from the following equation:        RSSI=−(10*n*log 10(d)+A),        -   where RSSI is the received power at the locator device, d is            the estimated distance between the target device and the            locator device, A is the transmit power from the target            device (which can be known in any suitable manner, such as            by being indicated in the received signal, by being known            based upon design parameters, etc.), and n is a signal            propagation constant that varies from environment to            environment. This signal propagation constant can range from            around 2 to 4, where 2 is a free-space value (e.g., no            obstruction, line of sight) and 4 represents a very lossy            environment. Thus, in determining the maximum distance, n            can be presumed to be 2 (or any other suitable value).    -   3. The locator device can periodically turn ON its GNSS receiver        and calculate its own position.    -   4. The locator device can wirelessly communicate certain system        settings to the target device to control the target device.    -   5. The target device can turn ON its GNSS receiver, calculate        its position, and, after calculating its position, transmits its        coordinates to the locator device.    -   6. After receiving the coordinates for the target device, the        locator device can calculate the approximate distance between        the locator device and the target device based on the two        coordinate pairs.    -   7. The locator device can compare the determined distance with        the maximum distance (“safe zone”) previously selected by the        user.    -   8. If the target device is determined to be within the safe zone        by at least some margin (e.g., 10%), the locator device can turn        OFF one or more components (e.g., the GNSS receiver, the radio        transceiver, etc.) of the locator device for some period of time        as well as transmit a message to the target device to do the        same.    -   9. After the period of time has elapsed, both the target device        and the locator device turn ON any suitable components and        repeat 2, 3, and 5-8 above.    -   10. If the target device is close to (e.g., within some margin        (e.g., 10%) of) the edge of, or outside of, the user-determined        “safe zone”, the locator device can vibrate as well as audibly        alert the user.    -   11. The locator device can calculate the direction from the        locator device to the target device based on the coordinates.    -   12. As shown in FIG. 4, the locator device's led screen can        display an arrow pointing to the location of the target device        based on the orientation of the locator device relative to the        Earth (which can be determined, e.g., using a tilt-compensated        compass) and the determined direction from the locator device to        the target device.    -   13. As also shown in FIG. 4, the locator device can additionally        display the distance between its current location and the        location of the target device in any suitable units (e.g.,        feet).    -   14. A user can use the arrow and the distance to find the        target.

Turning to FIG. 5, a flow diagram describing the operation of an exampleof a system in accordance with some embodiments is shown. Although thisexample illustrates a particular system relating to a child locator, itshould be apparent that what is described in this FIG. 5 can be used inother embodiments as well.

Beginning at 101, the system can be turned ON.

Next at 102, the locator device (described in connection with thisfigure as a Fob) can transmit a message to the target device (describedin connection with this figure as a Bracelet).

At 103, the Fob can determine the location of the Bracelet from RSSI asdescribed above.

At 104, the Fob can determine if whether the Bracelet is within the safezone (even accounting for a margin of error). If the Bracelet isdetermined to be within the safe zone, then, at 105, one or moreportions of the transceivers can power down to save battery charge, and,at 106, a user indicator can indicate that the child is in the safezone. At 108, a determination can be made as to whether a sleep interval(which can have any suitable duration) has been exceeded. If so, thepowered down portions can power back up at 109 and the process can loopback to 102.

If the Bracelet is determined to not be in the safe zone at 104, then at110 and 114, the Fob and the Bracelet can attempt to acquire a GNSS fix.

At 111, the process can determine if a fix was achieved by the Fob. Ifnot, at 112, the Fob user (e.g., the adult) can be instructed to gooutside. At 113, the user can move outside (which may be determined byreceiving an indication of a user button press) and then the process canloop back to 111.

At 115, the process can determine if a fix was achieved by the Bracelet.If not, at 116 the Bracelet can flash a home icon or otherwise indicateto the child that he/she should go home. At 117, the process candetermine if the child went outdoors (e.g., based on any suitableindicator such as detecting one or more satellites, a change intemperature, a change in light, etc.). If it is not determined that thechild has gone outdoors within a specified period of time, a failsafelocation mode can be activated at 118. Otherwise, if it is determinedthat the child has gone outdoors, the process can loop back to 115.

After it is determined at 107 that both the Fob and the Bracelet haveachieved a fix, at 119, a distance, relative direction, heading, speed,and any other suitable data can be calculated.

At 120, the process can determine whether a Find Mode has beenactivated. A Find Mode can be activated at 121 in response to an adultactivating it at 122 or a child pressing an alert button at 123. OnceFind Mode is activated, 110 and 114 can be performed as described above.

If it is determined at 120 that Find Mode has not been activated, thenat 124, the process can determine if the distance is in the safe zone.If so, then the process can branch to 105. If not, the process canactivate a compass in the Fob at 125 and then calculate a heading at126. Then, at 127, an arrow and distance to the Bracelet can then bepresented on the Fob as described above.

At 128, an adult can move toward the child's location. At 129, theprocess can determine whether the adult and the child are in the samelocation. If not, the process can loop back to 126. Otherwise, theprocess can determine if the Find Mode is still on at 130. If yes, theadult can be prompted to turn OFF Find Mode at 131 and process can loopback to 130. If no, the process can branch to 106.

In some embodiments, to increase battery life, the time during whichGNSS and radio receivers in the transceivers are turned ON can bereduced. In some embodiments, this can be performed based on the RSSIdistance measurements described above at 103 and 104. For example, ifthe maximum distance based on RSSI is calculated and it is determinedthat the target locator is not near the edge of the “safe zone” (whichis represented by a “yes” to 104) then the GNSS receivers can be keptOFF and rough measurements of distance based on RSSI used.

For example, assume that a user sets the safe zone to 1000 feet andremains stationary at a single location, such as a campsite. If anunsafe location (such as a road) to which a target (e.g., such as child)may attempt to go is 1500 feet from the home, an alarm can be generatedat some point well before the 1500-foot distance is reached based on anRSSI maximum distance measurement even with RSSI distance calculationerrors.

In some situations, object obstruction(s) may degrade transmitted radiopower enough that the Fob and Bracelet may be quite close but themaximum distance calculated from RSSI exceeds the user-determined safezone. For example, a child who is quite nearby may be hiding behind arock, through which the radio radiates quite poorly.

To address, this, in some embodiments, when it cannot be conclusivelydetermined from RSSI inference that the target device (e.g., a child) iswithin the safe zone (i.e., “no” at 104), the GNSS receivers on thelocator device and the target device can be turned “ON”, and a GNSSmeasurement of the distance between the locator device and the targetdevice (e.g., the adult and the child) can be calculated at 119.

Because saving battery charge is desirable, a power-down (or “sleepcycle”) can be calculated.

To determine the maximum time frame during which it is improbable forthe child to exceed the safe zone, the distance between his/her currentlocation and the nearest boundary of the safe zone can be calculated. Amaximum default travel rate, such as 5 mph (or any other suitablenumber) can be used for one or both of the adult and the child. Thescenario is considered in which the child immediately begins travelingtowards the nearest safe zone boundary. The time that it will take thechild to reach this boundary at the default travel rate can then becalculated. For example, if the adult and the child are only 70 feetaway from each other at a given point in time, the safe Zone is 1000feet, and only the child is assumed to be moving, a sleep cycle of atleast two minutes can be used as it would take 2.11 minutes to traverse930 feet at 5 mph.

As mentioned above, in some embodiments, a failsafe location mode can beactivated.

GNSS technology works poorly unless it has an unobstructed view of thesky. Except for unusual architecture, or very near to windows, it isusually not possible to obtain a usable GNSS signal indoors. This meansthat if the child moved to a location that presented an obstructed viewof the sky, a situation can be imagined in which the Fob and theBracelet can communicate via their RF link, and the Fob can determineits location, but the Bracelet cannot determine its own location.

For example, when a child goes inside of a house and remains there, theexact location of the child may not be possible to determine. In thiscase, the Fob can attempt to direct the adult to the last known recorded(“geocached”) location of the child. The Bracelet can in the meantimestill continue to search for a GNSS signal. If the Fob comes to thelocation of the last geocached location of the Bracelet and the Braceletis still unable to produce a GNSS fix, the failsafe location mode can beactivated.

In this mode, the Fob can direct the adult user to a series of points inorder to conduct a series of measurements of Bracelet radio strength(RSSI) that can be correlated with the Fob location to eventuallyproduce a meaningful approximation of the target location. In this mode,the Bracelet is assumed to be stationary. The adult can be directed asfollows:

“Adult User Actions in Failsafe Location Mode”

-   -   1. When the adult arrives at the last known location (L1), the        Fob can instruct the user to stop, use RSSI to produce an        approximate range of distance, and determine an approximate        distance, d1.    -   2. The Fob can then randomly determine a location (L2) that is        d1 away from the current location and direct the adult user to        it.    -   3. When the adult user reaches L2, the Fob can record RSSI, add        RSSI to the L2 listing in a table of measurements, and use this        measurement to produce an approximate distance to the Bracelet,        d2.    -   4. Next, the Fob can calculate a new location, L3, which is no        closer than d1 to L2 or L1.    -   5. By way of choosing a random location that satisfies this        condition, producing a vector, and displaying a corresponding        on-screen arrow, the Fob can instruct the user to move towards        new location, L3.    -   6. When the user arrives at L3, the Fob can record RSSI, add        RSSI to the L3 listing in a table of measurements, and use this        measurement to produce an approximate distance to the Bracelet,        d3.    -   7. The Fob can direct the adult user to repeat steps 4 and 5        until two or more data pairs (d4,L5), and d5,L5), etc., are        created.    -   8. Using any suitable non-linear fitting trilateration        technique, the Fob can determine the likely location of the        wearable to a certain degree of confidence.    -   9. If a location can be determined, the Fob can display an arrow        to this location. If a location cannot yet be determined to a        high degree of confidence, the Fob can repeat step

Any suitable non-linear fitting trilateration technique can be used insome embodiments. For example, a weighted nonlinear least squaresfitting technique, with weights inversely proportional to the squaredradii, can be used. For, example, the following code can be used inMathematica to compute the fit:fit=NonlinearModelFit[data,Norm[{x,y}−{x0,y0}],{x0,y0},{x,y},Weights→1/observations{circumflexover ( )}2]

For large radii, more accurate (spherical or ellipsoidal) solutions canbe found merely by replacing the Euclidean distance Norm[{x, y}−{x0,y0}] by a function to compute the spherical or ellipsoidal distance. InMathematica this could be done, e.g., viafit=NonlinearModelFit[data,GeoDistance[{x,y},{x0,y0}],{x0,y0},{x,y},Weights→1/observations{circumflexover ( )}2]

One advantage of using a statistical technique like this is that it canproduce confidence intervals for the parameters (which are thecoordinates of the device) and even a simultaneous confidence ellipsefor the device location. For example:ellipsoid=fit[“ParameterConfidenceRegion”,ConfidenceLevel→0.95];fit[“ParameterConfidenceIntervalTable”,ConfidenceLevel→0.95]

FIG. 6 provides an illustration of such a technique. As shown,

-   -   The squares are the (known) locations of a locator device, such        as L1, L2, L3, etc., at the moment that a corresponding distance        to target device was determined, e.g., d1, d2, d3, etc.,        respectively.    -   The triangle is the true device location.    -   The circles represent an area that is likely to contain a target        device, based on radii stored in the aforementioned table of        measurements as d1, d2, d3, etc. Ideally, they would all        intersect at the true device location—but obviously they do not,        due to measurement error inherent to inferring distance from        RSSI.    -   The hexagon is the estimated device location.    -   The dashed-line ellipse demarcates a 95% confidence region for        the device location.

The shape of the ellipse in this case is of interest: the locationaluncertainty is greatest along a NW-SE line. Here, the distances to threeaccess points (to the NE and SW) barely change and there is a trade-offin errors between the distances to the two other access points (to thenorth and southeast).

A more accurate confidence region can be obtained in some systems as acontour of a likelihood function; this ellipse is just a second-orderapproximation to such a contour.

When the radii are measured without error, all the circles will have atleast one point of mutual intersection and—if that point is unique—itwill be the unique solution.

The accuracy of this method increases by increasing the number oflocations (L N) at which a distance to target (d N) can be estimated.Three or more are needed to obtain confidence intervals. When only twoare available, it finds one of the points of intersection (if theyexist); otherwise, it selects an appropriate location between the twoaccess points and directs the user to walk to this new location.

In some embodiments, the locator device can be designed to be used inprimarily two orientations: hanging by an integral clip mechanism from abelt loop or backpack (perpendicular to the ground); and held in thepalm of an adult user, parallel to the ground.

RF communication devices that cannot rely on continued singularorientation between nodes can present a design challenge that is mostcommonly solved by utilizing antennas that are omnidirectional in theirradiation pattern. However, this solution is far from ideal when dealingwith a communication link between two pedestrians, since a great amountof energy is wasted into the ground and sky.

Highly directional antennas, such as a parabolic or yagi antenna, arealso not appropriate as they require a high degree of user compliance aswell as certainty about the location of the other transceiver andantenna.

Accordingly, in some embodiments, by using an onboard accelerometer toinfer orientation, an electronic antenna switch can be utilized todirect RF transmission and reception to one of two (or more) antennas,depending on which is most appropriate. Any suitable antenna type can beused to achieve any suitable beam pattern. For example, in someembodiments, a printed circular “panic button” antenna can be used todirect energy around the periphery of the device in a donut shapedpattern. As another example, in some embodiments, a patch antenna or aprinted inverted-L antenna can be used.

It should be understood that the above steps of the flow diagram of FIG.5 can be executed or performed in any order or sequence not limited tothe order and sequence shown and described in the figure. Also, some ofthe above steps of the flow diagram of FIG. 5 can be executed orperformed substantially simultaneously where appropriate or in parallelto reduce latency and processing times. Furthermore, it should be notedthat FIG. 5 is provided as an example only. At least some of the stepsshown in this figure may be performed in a different order thanrepresented, performed concurrently, or altogether omitted.

In some implementations, any suitable computer readable media can beused for storing instructions for performing the processes describedherein. For example, in some implementations, computer readable mediacan be transitory or non-transitory. For example, non-transitorycomputer readable media can include media such as magnetic media (suchas hard disks, floppy disks, etc.), optical media (such as compactdiscs, digital video discs, Blu-ray discs, etc.), semiconductor media(such as flash memory, electrically programmable read only memory(EPROM), electrically erasable programmable read only memory (EEPROM),etc.), any suitable media that is not fleeting or devoid of anysemblance of permanence during transmission, and/or any suitabletangible media. As another example, transitory computer readable mediacan include signals on networks, in wires, conductors, optical fibers,circuits, any suitable media that is fleeting and devoid of anysemblance of permanence during transmission, and/or any suitableintangible media.

The provision of the examples described herein (as well as clausesphrased as “such as,” “e.g.,” “including,” and the like) should not beinterpreted as limiting the claimed subject matter to the specificexamples; rather, the examples are intended to illustrate only some ofmany possible aspects.

Although the disclosed subject matter has been described and illustratedin the foregoing illustrative implementations, it is understood that thepresent disclosure has been made only by way of example, and thatnumerous changes in the details of implementation of the disclosedsubject matter can be made without departing from the spirit and scopeof the disclosed subject matter, which is limited only by the claim(s)that follow. Features of the disclosed implementations can be combinedand rearranged in various ways.

What is claimed is:
 1. A locator device for locating a target device,comprising: a first transceiver configured to communicate with a secondtransceiver in the target device; a receiver configured to receive datafrom a plurality of satellites for calculating a location; a visualindicator; and a hardware processor that: receives signals from thefirst transceiver; calculates a first estimated distance between thelocator device and a target device based on the signals; controlswhether the receiver is powered on or off based on the first estimateddistance; powers on the receiver after it has been powered off for aperiod of time, wherein the period of time is determined based on amaximum travel rate of the target device and a second estimated distancebetween the target device and a boundary; and causes the visualindicator to indicate an estimated direction to the target device fromthe locator device.
 2. The locator device of claim 1, wherein thehardware processor also controls whether a receiver of the target deviceis powered on or off based on the first estimated distance.
 3. Thelocator device of claim 1, wherein the hardware processor also controlswhether the first transceiver is powered on or off based on the firstestimated distance.
 4. The locator device of claim 1, wherein thehardware processor also powers on the first transceiver of the locatordevice after it has been powered off for the period of time.
 5. Thelocator device of claim 1, further comprising a plurality of antennascoupled to the first receiver by at least one switch, wherein thehardware processor also controls which of the plurality of antennas isused based on an orientation of the locator device.
 6. The locatordevice of claim 1, wherein the hardware processor also: determines thata location of the locator device is a current location; instructs a userof the locator device to move the locator device to a first new locationthat is the first estimated distance from the current location;calculates a first new distance estimate between the locator device anda target device at the first new location; instructs the user of thelocator device to move the locator device to a second new location thatis at least the first estimated distance from the first new location;calculates a second new distance estimate between the locator device anda target device at the second new location; instructs the user of thelocator device to move the locator device to a third new location thatis at least the first estimated distance from the second new location;calculates a third new distance estimate between the locator device anda target device at the third new location; instructs the user of thelocator device to move the locator device to a fourth new location thatis at least the first estimated distance from the third new location;calculates a fourth new distance estimate between the locator device anda target device at the fourth new location; and estimates a location ofthe target device based on the current location, the first new location,the second new location, the third new location, the fourth newlocation, the first estimated distance, the first new distance estimate,the second new distance estimate, the third distance estimate, and thefourth distance estimate.
 7. The locator device of claim 6, wherein thehardware processor estimates the location of the target device using anon-linear fitting trilateration technique.
 8. A method for locating atarget device, comprising: receiving signals from a first transceiver,of a locator device, configured to communicate with a second transceiverin the target device; calculating a first estimated distance between thelocator device and a target device based on signals received from thefirst transceiver; controlling whether a receiver configured to receivedata from a plurality of satellites for calculating a location ispowered on or off based on the first estimated distance; powering on thereceiver after it has been powered off for a period of time, wherein theperiod of time is determined based on a maximum travel rate of thetarget device and a second estimated distance between the target deviceand a boundary; and causing a visual indicator to indicate an estimateddirection to the target device from the locator device.
 9. The method ofclaim 8, further comprising controlling whether a receiver of the targetdevice is powered on or off based on the first estimated distance. 10.The method of claim 8, further comprising controlling whether the firsttransceiver is powered on or off based on the first estimated distance.11. The method of claim 8, further comprising powering on the firsttransceiver of the locator device after it has been powered off for theperiod of time.
 12. The method of claim 8, further comprisingcontrolling which of a plurality of antennas that are coupled to thefirst receiver by at least one switch is used based on an orientation ofthe locator device.
 13. The method of claim 8, further comprising:determining that a location of the locator device is a current location;instructing a user of the locator device to move the locator device to afirst new location that is the first estimated distance from the currentlocation; calculating a first new distance estimate between the locatordevice and a target device at the first new location; instructing theuser of the locator device to move the locator device to a second newlocation that is at least the first estimated distance from the firstnew location; calculating a second new distance estimate between thelocator device and a target device at the second new location;instructing the user of the locator device to move the locator device toa third new location that is at least the first estimated distance fromthe second new location; calculating a third new distance estimatebetween the locator device and a target device at the third newlocation; instructing the user of the locator device to move the locatordevice to a fourth new location that is at least the first estimateddistance from the third new location; calculating a fourth new distanceestimate between the locator device and a target device at the fourthnew location; and estimating a location of the target device based onthe current location, the first new location, the second new location,the third new location, the fourth new location, the first estimateddistance, the first new distance estimate, the second new distanceestimate, the third distance estimate, and the fourth distance estimate.14. The method of claim 13, wherein the location of the target device isestimated using a non-linear fitting trilateration technique.